US20180154155A1

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Publication number: US20180154155A1
Application number: US15/368,895
Authority: US
Inventors: James Keaveney; Ultan Horgan; Jeffrey Madden
Original assignee: Medtronic Ardian Luxembourg SARL
Current assignee: Medtronic Ardian Luxembourg SARL
Priority date: 2016-12-05
Filing date: 2016-12-05
Publication date: 2018-06-07
Also published as: EP3548138A1; CN110035793A; AU2017372705A1; WO2018106582A1; JP2020500607A

Abstract

Neuromodulation devices for delivering neuromodulation therapy to distal vascular portions and proximal vascular portions and associated systems and methods. A neuromodulation device can include an elongated shaft having a proximal portion and a distal portion, each portion being sized and shaped for simultaneous positioning and deployment within respective proximal and distal vascular portions of a human vasculature. The elongated shaft can have an outer cross-sectional dimension that decrementally changes towards the distal end. The elongated shaft can also have a plurality of sections, each section configured to be independently shaped upon deployment in the intended distal or proximal vascular portion.

Description

TECHNICAL FIELD

The present technology is related to neuromodulation devices. In particular, at least various embodiments of the present technology are related to neuromodulation devices for delivering neuromodulation energy to proximal vascular portions and distal vascular portions.

BACKGROUND

The sympathetic nervous system (SNS) is a primarily involuntary bodily control system typically associated with stress responses. Fibers of the SNS extend through tissue in almost every organ system of the human body and can affect characteristics such as pupil diameter, gut motility, and urinary output. Such regulation can have adaptive utility in maintaining homeostasis or in preparing the body for rapid response to environmental factors. Chronic activation of the SNS, however, is a common maladaptive response that can drive the progression of many disease states. Excessive activation of the renal SNS in particular has been identified experimentally and in humans as a likely contributor to the complex pathophysiology of hypertension, states of volume overload (e.g., heart failure), and progressive renal disease.

Sympathetic nerves of the kidneys terminate in the renal blood vessels, the juxtaglomerular apparatus, and the renal tubules, among other structures. Stimulation of the renal sympathetic nerves can cause, for example, increased renin release, increased sodium reabsorption, and reduced renal blood flow. These and other neural-regulated components of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone. For example, reduced renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome, (i.e., renal dysfunction as a progressive complication of chronic heart failure). Pharmacologic strategies to thwart the consequences of renal sympathetic stimulation include centrally-acting sympatholytic drugs, beta blockers (e.g., to reduce renin release), angiotensin-converting enzyme inhibitors and receptor blockers (e.g., to block the action of angiotensin II and aldosterone activation consequent to renin release), and diuretics (e.g., to counter the renal sympathetic mediated sodium and water retention). These pharmacologic strategies, however, have significant limitations including limited efficacy, compliance issues, side effects, and others.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present technology. For ease of reference, throughout this disclosure identical reference numbers may be used to identify identical or at least generally similar or analogous components or features.

FIG. 1 is an exploded view of a neuromodulation device configured in accordance with an embodiment of the present technology.

FIG. 2 is a side view of the distal portion of the neuromodulation device ofFIG. 1 in an expanded state in accordance with an embodiment of the present technology.

FIG. 3 is a side view of the distal portion of a neuromodulation device ofFIG. 1 positioned within a blood vessel in accordance with an embodiment of the present technology.

FIGS. 4-6 are enlarged views of braided regions of the distal portion of the neuromodulation device ofFIG. 1 configured in accordance with embodiments of the present technology.

FIGS. 7-9 are enlarged cross-sectional views of the distal portion of the neuromodulation device ofFIG. 1 taken along cross-sections7-7,8-8 and9-9 ofFIG. 1 in accordance with other embodiments of the present technology.

FIG. 10 is an isometric view of a distal portion of a neuromodulation device configured in accordance with another embodiment of the present technology.

FIG. 11 is a side view of the distal portion of the neuromodulation device ofFIG. 10 positioned within a blood vessel in accordance with another embodiment of the present technology.

FIG. 12 is an isometric view of a distal portion of a neuromodulation device configured in accordance with a further embodiment of the present technology.

FIGS. 13 and 14 are enlarged transverse cross-sectional views of portions of the distal portion of the neuromodulation device ofFIG. 12 configured in accordance with a further embodiment of the present technology.

FIG. 15 is a side view of the distal portion of the neuromodulation device ofFIG. 12 positioned within a blood vessel in accordance with a further embodiment of the present technology.

FIG. 16 is a partially schematic illustration of a neuromodulation system configured in accordance with an embodiment of the present technology.

FIG. 17 illustrates modulating renal nerves with a neuromodulation device described herein in accordance with an additional embodiment of the present technology.

FIG. 18 is a conceptual illustration of the sympathetic nervous system (SNS) and how the brain communicates with the body via the SNS.

FIG. 19 is an enlarged anatomic view of nerves innervating a left kidney to form the renal plexus surrounding the left renal artery.

FIGS. 20 and 21 are anatomic and conceptual views, respectively, of a human body depicting neural efferent and afferent communication between the brain and kidneys.

FIGS. 22 and 23 are anatomic views of the arterial vasculature and venous vasculature, respectively, of a human.

DETAILED DESCRIPTION

Neuromodulation devices and systems configured in accordance with several embodiments of the present technology can include a neuromodulation assembly having a variable outer cross-sectional dimension to deliver neuromodulation energy to both proximal vascular portions and distal vascular portions. In certain embodiments, an outer cross-sectional dimension of the neuromodulation assembly decrementally changes towards a distal end portion of the assembly. The neuromodulation assembly can include energy delivery elements configured to deliver neuromodulation energy to both a proximal vascular portion having a first diameter and a distal vascular portion having a second diameter less than the first diameter. Specific details of several embodiments of the present technology are described herein with reference toFIGS. 1-23. Although many of the embodiments are described with respect to devices, systems, and methods for intravascular renal neuromodulation, other applications and other embodiments in addition to those described herein are within the scope of the present technology. For example, at least some embodiments may be useful for intraluminal neuromodulation, for non-renal neuromodulation, and/or for use in therapies other than neuromodulation. In addition, embodiments of the present technology can have different configurations, components, and/or procedures than those shown or described herein. Moreover, a person of ordinary skill in the art will understand that embodiments of the present technology can have configurations, components, and/or procedures in addition to those shown or described herein, and that these and other embodiments can be without several of the configurations, components, and/or procedures shown or described herein without deviating from the present technology.

As used herein, the terms “distal” and “proximal” define a position or direction with respect to a clinician or a clinician's control device (e.g., a handle of a neuromodulation device). The terms, “distal” and “distally” refer to a position distant from or in a direction away from a clinician or a clinician's control device. The terms “proximal” and “proximally” refer to a position near or in a direction toward a clinician or a clinician's control device. The headings provided herein are for convenience only and should not be construed as limiting the subject matter disclosed.

Additionally, the term “distal vascular portion” refers to any distal portion of a vessel (e.g., renal artery) having a cross-sectional dimension less than a cross-sectional dimension of a proximal portion of the vessel, and/or a different vessel extending from the. In some embodiments, the distal vascular portion of the renal artery can refer to an auxiliary vessel, a branch of the renal artery (e.g., anterior and/or posterior), a suprarenal artery, and/or a segmental artery (e.g., superior, inferior, anterior, and/or posterior).

Further, the term “proximal vascular portion” refers to any proximal portion of a vessel (e.g., renal artery) having a cross-sectional dimension greater than a cross-sectional dimension of a distal portion of the vessel, and/or a different vessel extending from the vessel. In some embodiments, the proximal vascular portion of the renal artery can refer to the superior vena cava, left brachiocephalic vein, right brachiocephalic vein, azygos vein, azygos arch, or other vessel suitable for neuromodulation therapy.

I. Selected Embodiments of Neuromodulation Devices and Assemblies for Proximal Vascular Portions and Distal Vascular Portions and Associated Methods

FIG. 1 is an exploded view of aneuromodulation device100 in accordance with an embodiment of the present technology, including a partially schematic enlarged isometric view of a distal portion of the device. Theneuromodulation device100 includes ahandle108, anelongated shaft110 having aproximal portion110aand adistal portion110b, and aneuromodulation assembly120 at thedistal portion110bof theelongated shaft110. Theelongated shaft110 and theneuromodulation assembly120 can be 2, 3, 4, 5, 6, or 7 French size or one or more other suitable catheter sizes. Theneuromodulation assembly120 includes a plurality ofenergy delivery elements124 mounted on asupport member122 that can be shaped into a desired configuration in operation. Thesupport member122 is configured to position theenergy delivery elements124 in both a proximal vascular portion and a distal vascular portion at the same time.

In the embodiment illustrated inFIG. 1, theneuromodulation assembly120 includes at least afirst section130 and asecond section140 distal to thefirst section130 with both sections extending along a length of thesupport member122. In the embodiment shown inFIG. 1, theenergy delivery elements124 are present in both thefirst section130 and thesecond section140. In other embodiments, thesupport member122 can include more sections than thefirst section130 and thesecond section140.

In some embodiments, as illustrated inFIG. 3, the first outercross-sectional dimension136 is sized and shaped to facilitate formation of an expanded state that accommodates an inner diameter of a typical renal artery (e.g., about 2-10 mm), and the second outercross-sectional dimension146 sized and shaped to facilitate formation of an expanded state that accommodates an inner diameter of a distal vascular portion, such as the distal vascular portion of the renal artery (e.g., about 0.25-5 mm). The third outercross-sectional dimension156 can be sized and shaped to facilitate formation of an expanded state that accommodates the inner diameter more distally along distal vascular portion (e.g., about 0.1-2 mm). In other embodiments, thesupport member122 can have other outer cross-sectional dimensions depending on the body lumen within which it is configured to be deployed. The outer cross-sectional dimensions described herein can be measures of cross-sectional areas, diameters, transverse dimensions or other measures of size.

Thesupport member122 can comprise a wall126 (e.g., a circumferential wall), a hollow ortubular core127 within thewall126, alumen128 within thecore127, and anatraumatic tip138. See e.g.FIGS. 7-9. Thelumen128 can extend distally from a proximal opening in thehandle108 or from a side port (not shown) along theshaft110 through thesupport member122. As illustrated inFIG. 1, theenergy delivery elements124 are positioned along thewall126. Thewall126 can be made from one or more materials (e.g., metals and/or polymers) formed into different arrangements (e.g., a braid or a mesh) suitable for supporting theenergy delivery elements124. Thewall126 and/or thecore127 can include a shape-memory memory material, such as a nickel-titanium alloy, suitable for imparting a shape to thesupport member122 when expanded (e.g., deployed state). In the illustrated embodiment, thecore127 includes a shape memory material, such as nitinol, that tends to form thesupport member122 into a desired configuration within a vessel. In other embodiments, the shape memory material is integrated into a portion of thewall126, e.g., a braided shape memory layer over-molded or encapsulated within a polymeric material. Thelumen128 is configured to receive a wire (e.g., a guidewire, a lead wire, etc.) or a plurality of such wires extending from theproximal portion110aof theelongated shaft110 into theneuromodulation assembly120 at thedistal portion110b. In some embodiments, theneuromodulation assembly120 can have a plurality of lumens and each lumen can be configured to carry a wire or plurality of wires (e.g., guidewire, lead wire, etc.). In one embodiment, the guidewire holds thesupport member122 in a non-expanded state for delivery (e.g., linear, straight, etc.), and upon removing the guidewire thesupport member122 expands into a desired shape (e.g., spiral) imparted by the shape-memory core127. In other embodiments, thesupport member122 can expand to a desired deployed shape upon releasing thesupport member122 from being radially constrained within a sheath by withdrawing the sheath and/or pushing thesupport member122.

In the embodiment illustrated inFIG. 1, theneuromodulation assembly120 includes six energy delivery elements124 (individually identified byreference numbers124a-f). In other embodiments, theneuromodulation assembly120 can include a different number of energy delivery elements124 (e.g., 1, 2, 8, 12, etc.). One or more of theenergy delivery elements124 can be electrodes configured to deliver therapeutic levels of RF energy and/or other forms of electrical energy to the vessel wall to ablate the nerves proximate to the treatment site. Theenergy delivery elements124 can be configured to deliver power either together or independently of each other in a monopolar fashion, either simultaneously or sequentially, and/or may deliver power between any desired combination of the elements in a bipolar fashion. In some embodiments, the energy delivery elements can be configured to deliver correspondingly less energy to nerves along a distal vascular portion to avoid damaging the increasingly fragile tissues. Additionally, a first therapeutic neuromodulation energy can be delivered to one set of the energy delivery elements124 (e.g., energy deliverelements124a-d), while a second therapeutic neuromodulation energy can be delivered to another set of energy delivery elements (e.g.,energy delivery elements124d-f). The second therapeutic neuromodulation energy can be less than the first therapeutic neuromodulation energy to protect smaller, more sensitive structures in the distal vascular portion. Theenergy delivery elements124 can also be configured to deliver constant power and/or monitor impedance indicating whether the energy delivery element(s)124 are contacting the vessel wall.

Theenergy delivery elements124 are spaced apart from each other along a length of thesupport member122. In the embodiment shown inFIG. 1, for example, energy deliverelements124a-care spaced apart from each other along thefirst section130 and energy deliverelements124d-fare spaced apart from each other along thesecond section140. Theenergy delivery elements124 can be arranged along thesupport member122 in a variety of patterns. For example, in the expanded state theenergy delivery elements124 can be positioned in multiple planes and on multiple sites across thesupport member122. Theenergy delivery elements124 may be mounted about, adhered to, and/or woven into thewall126. In several embodiments, theelectrodes124 can be formed of gold in accordance with electrodes of existing neuromodulation devices. Eachenergy delivery element124 can be electrically coupled to a pair of lead wires. In each pair, a copper wire can be used for conducting electrical power for neuromodulation and a constantan wire can form a thermocouple at theenergy delivery element124 for temperature monitoring.

As illustrated inFIG. 1, the firstenergy delivery element124ahas a firstcross-sectional dimension125aand each of the otherenergy delivery elements124b-fhas a decrementally changingcross-sectional dimension125b-f, respectively, in the distal direction. For example, thecross-sectional dimension125aof the firstenergy delivery element124ais greater than thecross-sectional dimension125bof the secondenergy delivery element124b, which is greater than thecross-sectional dimension125cof the thirdenergy delivery element124c, and so on to the lastenergy delivery element124f.

The outer cross-sectional dimension of thesupport member122 can be related to the number of pairs of lead wires carried by thewall126 at any particular longitudinal location. For example, the outer

cross-sectional dimensions

136,146 and156 are partially determined by the number of lead wires carried by thewall126. Each of the outer cross-sectional dimensions (e.g.,136,146 and156) relates to a combined cross-sectional area of the pairs of lead wires extending through theneuromodulation assembly120 at each cross-sectional area (e.g.,FIG. 7 shows six pairs at outer crosssectional dimension136,FIG. 8 shows three pairs at second outercross-sectional dimension146, andFIG. 9 shows one pair at the third outer cross sectional dimension156). As such, the number of pairs of lead wires carried by thesupport member122 decreases by one pair fromenergy delivery element124atoenergy delivery element124b, fromenergy delivery element124btoenergy delivery element124c, and so on toenergy delivery element124f.

One or more sensors (not shown), such as one or more temperature (e.g., thermocouple, thermistor, etc.), impedance, pressure, optical, flow, chemical, and/or other sensors, may be located proximate to, within, or integral with theenergy delivery elements124. The sensor(s) and theenergy delivery elements124 can be connected to one or more supply wires or optical fibers (not shown) that transmit signals from the sensor(s).

In other embodiments, theneuromodulation device120 can include other electrodes, transducers, or other elements to deliver energy to modulate nerves using other suitable neuromodulation modalities, such as pulsed electrical energy, microwave energy, optical energy, ultrasound energy (e.g., intravascularly delivered ultrasound, and/or high-intensity focused ultrasound (HIFU)), direct heat energy, radiation (e.g., infrared, visible, and/or gamma radiation), and/or other suitable types of energy. For example, some of theenergy delivery elements124 can be defined by radiation emitters that expose target nerves to radiation at a wavelength that causes a previously administered photosensitizer to react, such that it damages or disrupts the nerves. The radiation emitters can be optical elements coupled to fiber optic cables (e.g., extending through the elongated shaft110) for delivering radiation from a radiation source (e.g., an energy generator) at an extracorporeal location to the target tissue at the vessel, or may be internal radiation sources (e.g., LEDs) that are electrically coupled to a power source at an extracorporeal location via electrical leads within theelongated shaft110. In embodiments where one or more of theenergy delivery elements124 are defined by radiation emitters, a photosensitizer (e.g., oxytetracycline, a suitable tetracycline analog, and/or other suitable photosensitive compounds that preferentially bind to neural tissue) can be administered to a patient (e.g., orally, via injection, through an intravascular device, etc.), and preferentially accumulate at selected nerves (e.g., rather than other tissues proximate to the selected nerves). For example, more of the photosensitizer can accumulate in perivascular nerves around a blood vessel than in the non-neural tissues of the blood vessel. The mechanisms for preferentially accumulating the photosensitizer at the nerves can include faster uptake by the nerves, longer residual times at the nerves, or a combination of both. After a desired dosage of the photosensitizer has accumulated at the nerves, the photosensitizer can be irradiated usingenergy delivery elements124. Theenergy delivery elements124 can deliver radiation to the target nerves at a wavelength that causes the photosensitizer to react such that it damages or disrupts the nerves. For example, the photosensitizer can become toxic upon exposure to the radiation. Because the photosensitizer preferentially accumulates at the nerves and not the other tissue proximate the nerves, the toxicity and corresponding damage is localized primarily at the nerves. This form of irradiative neuromodulation can also or alternatively be incorporated in any one of the neuromodulation assemblies described herein. Further details and characteristics of neuromodulation assemblies with radiation emitters are included in U.S. patent application Ser. No. 13/826,604, which is incorporated herein by reference in its entirety.

FIG. 2 is a isometric view of thedistal portion110bof theneuromodulation assembly120 in an expanded state in accordance with an embodiment of the present technology. In the illustrated embodiment, thesupport member122 has a spiral shape imparted to both thefirst section130 and thesecond section140 by theshape memory core127. The spiral shape of thesupport member122 extends around an imaginary longitudinalcentral axis170 and extends from an imaginary cross-sectional plane into three dimensions. The spiral shape is imparted by thecore127 after the guidewire is removed (e.g., retracted) from thelumen128 of thedistal portion110bof theelongated shaft110. In other embodiments, the shape can be imparted on at least one other portion of thesupport member122.

FIG. 3 is a side view of thedistal portion110bof a neuromodulation device positioned within both a proximal vascular portion (e.g., a main renal artery) and a distal vascular portion (e.g., a renal branch vessel in this example) in accordance with an embodiment of the present technology. In operation, theneuromodulation assembly120 is intravascularly delivered to a treatment site within both the proximal vascular portion vessel and the distal vascular portion in a single act of positioning theneuromodulation assembly120. As illustrated, thesupport member122 extends from the proximal vascular portion into the distal vascular portion and is designed to apply a desired outward radial force to the vessel walls when deployed and expanded into the spiral shape. The deployedsupport member122 can be configured and positioned such that theenergy delivery elements124a-dare pressed against the interior wall of the proximal vascular portion and the

energy delivery elements

124eand124fare pressed against the interior wall of the distal vascular portion. In other embodiments, theneuromodulation assembly120 is positioned such that fewer ofenergy delivery elements124 contact the proximal vascular portion, such asenergy delivery elements124a-c, while more of theenergy delivery elements124d-fcontact the distal vascular portion. Theenergy delivery elements124 deliver therapeutic neuromodulation energy to nerves proximate to the treatment site(s) at the interior wall(s) of the blood vessel(s), which is expected to modulate or ablate nerves at the treatment site (e.g., both efferent renal nerves and afferent renal nerves) and/or proximate to the treatment site.

Several embodiments of theneuromodulation assembly120 shown inFIGS. 1-3 are expected to provide efficient, enhanced neuromodulation in anatomical structures with different sizes. Since thefirst section130 of theneuromodulation assembly120 is configured to deliver energy to areas of a proximal vascular portion having a first structure (e.g., a main renal artery) and thesecond section140 is configured to deliver energy to areas of a distal vascular portion having a second structure (e.g., a more distal portion of the main renal artery or a renal branch vessel) that would otherwise not be accessible by a device suitable for only the first structure of the proximal vascular portion, theneuromodulation assembly120 is expected to enhance the ablation of nerves adjacent the different vascular structure, and in particular renal nerves. Moreover, several embodiments of theneuromodulation assembly120 enable such dual neuromodulation in a single deployment using a single device. This saves time and reduces challenges with positioning and repositioning devices in the renal vasculature.

FIGS. 7-9 are partially schematic enlarged cross-sectional views of the distal portion of the neuromodulation device ofFIG. 1 taken along cross-sections7-7,8-8 and9-9 ofFIG. 1, respectively, that show additional features of lead wire pairs220. Theneuromodulation assembly120 can include various features generally similar to those of theneuromodulation assembly120 described above with reference toFIGS. 1-6, and like reference numbers refer to common components inFIGS. 1-9. For example,FIG. 7 illustrates the lead wire pairs220a-fintegrated into one portion of thewall126 at a proximal portion of thesupport member122, andFIGS. 8 and 9 show cross-sections progressively more distally along thesupport member122 with progressively fewer lead wire pairs220. The lead wires220 can be braided into abraided structure210 of thewall126 as explained above with reference toFIGS. 4-6, or the lead wire pairs220 can be in lumens or channels extending through thewall126 with each lead wire in a separate lumen or a plurality of lead wires in a single lumen.

FIG. 10 is a partially schematic enlarged isometric view of a distal portion of aneuromodulation assembly1020 in accordance with another embodiment of the present technology. Theneuromodulation assembly1020 can include various features generally similar to those described above with reference toFIGS. 1-9, and like reference numbers refer to like components inFIGS. 1-10. In this embodiment, theneuromodulation assembly1020 has asupport structure1022 including afirst section1030, asecond section1040, and anintermediate section1050 between the first and

second sections

1030 and1040. In the embodiment shown inFIG. 10, thefirst section1030 of thesupport member1022 is configured to have a first shape (e.g. spiral), thesecond section1040 of thesupport member1022 is configured to have a second shape (e.g., spiral), and theintermediate section1050 between the first and

second sections

1030 and1040 can have third shape different than the first and second shapes. Theintermediate section1050, for example, can be at least substantially linear. The shapes of thefirst section1030,second section1040 andintermediate section1050 can be imparted to thesupport member122 by thecore127 following at least partial removal (e.g., retraction) of a guidewire from thelumen128 as theneuromodulation assembly120 is being deployed. The spiral shape of thefirst section1030 and thesecond section1040 extends around an imaginary longitudinalcentral axis1060 and extends from an imaginary transverse plane into three dimensions. Alternatively, each section of thesupport member1022 can have a different shape. Shapes other than those illustrated and described herein can be imparted to thesupport member1022 in an expanded state.

Thefirst section1030 can be sized and shaped to accommodate positioning and deployment in a first vascular portion having an inner diameter of, e.g., about 2-10 mm, and thesecond section1040 is sized and shaped to be positioned in a second vascular portion having an inner diameter of, e.g., about 0.25-5 mm or about 0.1-2 mm. The outer cross-sectional dimension of thesupport member1022 decreases (e.g., constantly or step-wise) distally, and in particular the outer cross-sectional dimension of thesecond section1040 is less than that of thefirst section1030. As described above, the outer cross-sectional dimension(s) (e.g.,136,146 and156) are partially based on a cross-sectional dimension of a pair, or number of pairs, of lead wire pairs220 carried by thewall126 of thesupport member1022.

As illustrated inFIG. 10,energy delivery elements124g-jare disposed along a length of thesupport member1022. AlthoughFIG. 10 illustrates two

energy delivery elements

124gand124hlocated in thefirst section1030 and two

energy delivery elements

124iand124jlocated in thesecond section1040, additional energy delivery elements can be disposed within thefirst section1030 and/or thesecond section1040. As described above, theenergy delivery elements124g-jeach have across-sectional dimension125g-j, respectively, that decrementally changes distally along thesupport member1022. In the illustrated embodiment, theneuromodulation assembly1020 includes anenergy delivery element124kdisposed at thetip138 having across-sectional dimension125k. Alternatively, thetip138 can be an atraumatic tip.

FIG. 11 is a side view of theneuromodulation assembly1020 ofFIG. 10 positioned within a blood vessel in accordance with an embodiment of the present technology. In the illustrated embodiment, theneuromodulation assembly1020 is expanded and deployed in the proximal vascular portion and the distal vascular portion at the same time. As a result, theneuromodulation assembly1020 can be intravascularly delivered to at least two treatment sites having different structures (e.g., different diameters) in a single deployment of theneuromodulation assembly1020. This allows theenergy delivery element124gto be positioned to deliver energy to ablate nerves along the proximal vascular portion (e.g., a portion of the main renal artery) of the patient, whereas theenergy delivery element124iis positioned to deliver energy to ablate nerves along the distal vascular portion (e.g., an anterior branch of the renal artery of the patient). Similarly, theenergy delivery element124kcan be positioned to deliver energy to ablate renal nerves even more distally along the vessel. In other embodiments, theenergy delivery element124 can be positioned differently than shown inFIG. 11. Theintermediate section1050 can be positioned at a distal portion of the main renal artery and extend to or through a proximal portion of the branch vessel to support positioning of thefirst section1030 and thesecond section1040 at the desired locations in the proximal vascular portion (e.g., main renal artery) and the distal vascular portion (e.g., branch vessel), respectively.

FIG. 12 is an isometric view of a distal portion of aneuromodulation assembly1220 with an enlarged view of one portion of theneuromodulation assembly1220 in accordance with yet another embodiment of the present technology. Theneuromodulation assembly1220 can include a number of features generally similar to those described above with reference toFIGS. 1-11, and like reference numbers refer to similar components inFIGS. 1-12. In this embodiment, however, theneuromodulation assembly1220 has asupport member1222 including afirst section1230 and asecond section1240 that is slidably received within thefirst section1230. For example, thefirst section1230 of thesupport member1222 is defined by a portion of thedistal end110b(FIG. 1) of the elongated shaft110 (FIG. 1), and thesecond section1240 is defined by a distal portion of aguidewire1210 that passes through theelongated shaft110. Theguidewire1210 can thus be advanced or retracted while positioning theneuromodulation assembly1220 within the patient's vessel. The illustratedguidewire1210 has anatraumatic tip1212, and in some embodiments, theatraumatic tip1212 can have a shape (e.g., a hockey tip) configured to direct (e.g., steer) theneuromodulation assembly1220 during positioning inside the patient's vessel lumen.

FIG. 12 illustrates theneuromodulation assembly120 in a linear (e.g., straight) configuration for delivery into the patient's vessel(s). Similar to the other embodiments of the

neuromodulation assemblies

120 and1020 described above with respect toFIGS. 1-11, a shape (e.g., helical, spiral, linear, etc.), or a plurality of shapes, can be imparted to theneuromodulation assembly1220 ofFIG. 12 when expanded. In some embodiments, the shape can be imparted to each section (first section1230 and second section1240) of thesupport member1222 independently of the other sections. Thecore127 in thefirst section1230 of thesupport member1222 can include a shape memory material, e.g., nitinol, configured to impart the desired shape to thefirst section1230 upon expansion. Additionally, a portion of theguidewire1210 can be formed from a shape memory material, e.g., nitinol. For example, the distal portion of theguidewire1210 with theenergy delivery elements124land124mcan be made from a shape-memory material, while the more proximal portion of theguidewire1210 can be an elastic material without shape memory. Since theguidewire1210 can be made from a combination of shape-memory material and elastic non-memory material, theneuromodulation assembly1220 can be retained in the straight position shown inFIG. 12 by a sheath.

FIG. 13 is a side view of theneuromodulation assembly1220 ofFIG. 12 in a deployed state within the vasculature of a patient. In operation, theneuromodulation assembly1220 is positioned so that the distal end of thefirst section1230 is located at or near the transition from a proximal vascular portion (e.g., the main renal artery) to a distal vascular portion (e.g., a branch of main the renal artery) while theneuromodulation assembly1220 is within a sheath. Theguidewire1210 is then advanced from the through adistal opening1226 of thefirst section1230. In this embodiment, theguidewire1210 extends from thedistal opening1226 and into the distal vascular portion (e.g., branch of the main renal artery) where it forms into a spiral or other suitable shape for pressing theenergy delivery elements124land124magainst the wall of the distal vascular portion. Thefirst section1230 of theneuromodulation assembly1220 is then deployed by withdrawing the sheath (not shown). Theneuromodulation assembly1220 can accordingly be positioned at a plurality of treatment sites having different sizes and shapes in a single deployment (e.g., at the same time). For example, when positioned, thefirst section1230 is expanded into the deployed state at one treatment site and thesecond section1240 is expanded at another treatment site by releasing theguidewire1210 from thelumen128. In other embodiments, other suitable positioning methods and deployment methods can be used to position and deploy theneuromodulation assembly1220.

In the embodiment shown inFIG. 13, thefirst section1230 of the deployedsupport member1222 has a spiral shape configured to press theenergy delivery elements124a-dagainst the interior wall of the proximal vascular portion (e.g., main renal artery) to contact the first treatment site. Thesecond section1240 of thesupport member1222 also has a spiral shape configured to press theenergy delivery elements124land124magainst the interior wall of the distal vascular portion to contact the second treatment site. Thefirst section1230 is designed to apply the desired outward radial force to the proximal vascular portion, whereas thesecond section1240 is designed to apply the desired outward radial force to the distal vascular portion. The desired outward radial force applied to the proximal vascular portion can be greater than the desired outward radial force applied to the distal vascular portion to avoid damaging the distal vascular portion by applying too much outward radial force.

Theenergy delivery elements124a-dand124l-minFIG. 13 are each electrically coupled to leadwire pairs1410a-dand1410l-m, respectively, shown inFIGS. 14 and 15. Thelead wire pairs1410a-dcan be carried by thefirst section1230 of thesupport member1222, and the lead wire pairs1410l-mcan be carried by the second section1240 (e.g., the guidewire1210) of thesupport member1222. In certain embodiments, theenergy delivery elements124a-dcan deliver a first therapeutic neuromodulation energy to nerves proximate to a first treatment site in the proximal vascular portion, and the energy deliver elements124l-mcan deliver a second therapeutic neuromodulation energy to the nerves proximate to a second treatment site in the distal vascular portion. The second therapeutic neuromodulation energy can be less than the first therapeutic neuromodulation energy to avoid damaging the distal vascular portion, nerves distal from the second treatment site, and/or adjacent tissue.

FIGS. 14 and 15 are partially schematic enlarged cross-sectional views of the distal portion of the neuromodulation device ofFIG. 12 taken along cross-sections14-14 and15-15 ofFIG. 12. For example,FIG. 14 illustrates a cross-sectional view of theneuromodulation assembly1220 at the first outer cross-sectional dimension136 (FIG. 13). In this embodiment, theguidewire1210 extends through at least a portion of thelumen128 of theneuromodulation assembly1220. As illustrated, theguidewire1210 has anouter layer1420, amiddle layer1421, an inner layer1422 (e.g., silver nickel), and alumen1423. Theouter layer1420 is formed of cobalt chromium for push/pull axial strength along theguidewire1210. Themiddle layer1421 is formed of tantalum for radiopacity. In the illustrated embodiment, thelumen1423 of theguidewire1210 is formed by cutting aslot1426 having sidewalls1424 through the outer, middle and

inner layers

1420,1421,1422 along at least a portion of the length of theguidewire1210 and then etching a central portion of the remaining material of theinner layer1422. Theslot1426 can be formed using a laser, and the central region of theinner layer1422 can be removed using a chemical etching process (e.g., a liquid chemical etch). In some embodiments, the layers can be formed using any material, or materials, suitable to perform at least similar functions of those described above. Thelumen1423 is sized and shaped to retain lead wires coupled to energy delivery elements disposed on theguidewire1210. As illustrated, twolead wire pairs1410land1410mare in thelumen1423, and thelead wire pairs1410land1410mare electrically coupled toenergy delivery elements124land124mdisposed at the third section1250 (e.g., the distal portion of the guidewire1210). In other embodiments, thelumen1423 can be sized and shaped to retain a number of pairs of lead wires sufficient to electrically couple to eachenergy delivery element124 disposed on theguidewire1210.

FIG. 15 illustrates a cross-sectional view of the neuromodulation assembly at the third outercross-sectional dimension1260. The third outercross-sectional dimension1260 is distal to the distal opening1226 (FIG. 12) and includes theguidewire1210. The outer cross-sectional dimension of theguidewire1210 shown inFIG. 15 is therefore smaller than an outer cross-sectional dimension of thefirst portion1230 shown inFIG. 14. Similar toFIG. 14, thelumen1423 of the guidewire contains the two pairs oflead wires1410land1410m.

Although the embodiments of the

neuromodulation assemblies

120,1020 and1220 shown inFIGS. 1-15 have partially spiral/helically-shaped configurations and partially linear configurations, spiral/helically-shaped configurations, or linear configurations, in other embodiments, the neuromodulation assemblies can have other suitable shapes, sizes, and/or configurations. For example, in further embodiments, thedistal portion110bof the elongated shaft110 (FIG. 1) can have other suitable shapes (e.g., semi-circular, curved, straight, etc.), and/or the neuromodulation assemblies can include multiple support members configured to carry one or moreenergy delivery elements124, e.g., electrodes. Other suitable devices and technologies are described in, for example, U.S. patent application Ser. No. 12/910,631, filed Oct. 22, 2010; U.S. patent application Ser. No. 13/279,205, filed Oct. 21, 2011; U.S. patent application Ser. No. 13/279,330, filed Oct. 23, 2011; U.S. patent application Ser. No. 13/281,360, filed Oct. 25, 2011; U.S. patent application Ser. No. 13/281,361, filed Oct. 25, 2011; PCT Application No. PCT/US11/57754, filed Oct. 25, 2011; U.S. Provisional Patent Application No. 61/646,218, filed May 5, 2012; U.S. patent application Ser. No. 13/793,647, filed Mar. 11, 2013; U.S. Provisional Patent Application No. 61/961,874, filed Oct. 24, 2013; and U.S. patent application Ser. No. 13/670,452, filed Nov. 6, 2012. All of the foregoing applications are incorporated herein by reference in their entireties. Non-limiting examples of devices and systems include the Symplicity Flex™ and the Symplicity Spyral™ multielectrode RF ablation catheter.

II. Selected Examples of Neuromodulation Devices and Related Systems

FIG. 16 is a partially schematic illustration of a therapeutic system1600 (“system1600”) configured in accordance with an embodiment of the present technology. Thesystem1600 can be used in conjunction with embodiments of the

neuromodulation assemblies

120,1020 and1220 described above with references toFIGS. 1-15 to deliver neuromodulation therapy. In addition, thesystem1600 can be used to provide the autonomic modulation therapy of the methods described herein.

As shown inFIG. 16, thesystem1600 can include aneuromodulation device1602 that includes thehandle108, theelongated shaft110 having adistal portion110bconfigured to be positioned at a target site within the renal artery, and any of the

neuromodulation assemblies

120,1020 and1220 described above. In some embodiments, theelongated shaft110, at least twoenergy delivery elements124, and at least two pairs of lead wires220 are integral components of a single catheter (not shown) configured for delivering neuromodulation energy to treatment sites in both a proximal vascular portion and a distal vascular portion that have different sizes and/or shapes. In other embodiments,elongated shaft110, at least twoenergy delivery elements124, and at least two pairs of lead wires220 can be components of more than one catheter (not shown). In the illustrated embodiment, thesystem1600 can further include aconsole1604 and acable1606 extending between theconsole1604 and thehandle108. Theconsole1604 can be configured to control, monitor, supply, and/or otherwise support operation of theneuromodulation device1602. In addition, theconsole1604 can be configured to provide feedback to an operator before, during, and/or after a treatment procedure via an evaluation/feedback algorithm1616.

Theconsole1604 can further be configured to generate a selected form and/or magnitude of energy for delivery to tissue at the treatment site via the

neuromodulation assemblies

120,1020 and1220, and therefore theconsole1604 may have different configurations depending on the treatment modality of theneuromodulation device1602. For example, when theneuromodulation device1602 is configured for electrode-based, heat-element-based, or transducer-based treatment, theconsole1604 can include an energy generator1610 (shown schematically) configured to generate radio frequency (RF) energy (e.g., monopolar and/or bipolar RF energy), pulsed energy, microwave energy, optical energy, ultrasound energy (e.g., intravascularly delivered ultrasound and/or high-intensity focused ultrasound (HIFU)), direct heat energy, radiation (e.g., infrared, visible, and/or gamma radiation), and/or another suitable type of energy. In this configuration, theconsole1604 can also include evaluation/feedback algorithms1616 for controllingenergy delivery elements124 of

neuromodulation assemblies

120,1020 and1220. If the impedance changes during energy delivery, the power can be adjusted at thegenerator1610. In selected embodiments, thegenerator1610 can be configured to deliver a monopolar electric field via one or more of theenergy delivery elements124. In such embodiments, a neutral ordispersive electrode1630 may be electrically coupled to thegenerator1610 and attached to the exterior of the patient. When theneuromodulation device1602 is configured for cryotherapeutic treatment, theconsole1604 can include a refrigerant reservoir (not shown), and can be configured to supply theneuromodulation device1602 with refrigerant. Similarly, when theneuromodulation device1602 is configured for chemical-based treatment (e.g., drug infusion), theconsole1604 can include a chemical reservoir (not shown) and can be configured to supply theneuromodulation device1602 with one or more chemicals.

In various embodiments, thesystem1600 can further include acontroller1614 communicatively coupled to theneuromodulation device1602. Thecontroller1614 can be configured to initiate, terminate, and/or adjust operation of one or more components (e.g., the energy delivery elements124) of theneuromodulation device1602 directly and/or via theconsole1604 and/or via a wired or wireless communication link. In various embodiments, thesystem1600 can include multiple controllers. In other embodiments, theneuromodulation device1602 can be communicatively coupled to asingle controller1614. The controller(s)1614 can be integrated with theconsole1604 or thehandle108 positioned outside the patient and used operate thesystem1600. In other embodiments, thecontroller1614 can be omitted or have other suitable locations (e.g., within thehandle108, along thecable1606, etc.). Thecontroller1614 can include computer-implemented instructions to initiate, terminate, and/or adjust operation of one or more components of theneuromodulation device1602 directly and/or via another aspect of the system (e.g., the console or handle108). For example, thecontroller1614 can further provide instructions to theneuromodulation device1602 to apply neuromodulatory energy to the treatment site (e.g., RF energy via the energy delivery elements124). Thecontroller1614 can be configured to execute an automated control algorithm and/or to receive control instructions from an operator. Further, thecontroller1614 can include or be linked to the evaluation/feedback algorithm1616 that can provide feedback to an operator before, during, and/or after a treatment procedure via a console, monitor, and/or other user interface.

FIG. 17 (with additional reference toFIG. 16) illustrates modulating renal nerves in accordance with an embodiment of thesystem1600. Theneuromodulation device1602 provides access to the renal plexus RP through an intravascular path P, such as a percutaneous access site in the femoral (illustrated), brachial, radial, or axillary artery to a targeted treatment site within a respective renal artery RA. By manipulating theproximal portion110aof theelongated shaft110 from outside the intravascular path P, a clinician may advance theelongated shaft110 through the sometimes tortuous intravascular path P and remotely manipulate thedistal portion110b(FIG. 16) of theelongated shaft110. In the embodiment illustrated inFIG. 17, theneuromodulation assembly120 is delivered intravascularly to the treatment site using aguidewire1736 in an OTW technique. At the treatment site, theguidewire1736 can be at least partially withdrawn or removed, and theneuromodulation assembly120 can transform or otherwise be moved to a deployed arrangement for recording neural activity and/or delivering energy at the treatment site. In other embodiments, theneuromodulation assembly120 may be delivered to the treatment site within a guide sheath (not shown) with or without using theguidewire1736. When the

neuromodulation assemblies

120,1020 and1220 are at the treatment site, the guide sheath may be at least partially withdrawn or retracted and the

neuromodulation assemblies

120,1020 and1220 can be transformed into the deployed arrangement. In other embodiments, theelongated shaft110 may be steerable itself such that the

neuromodulation assemblies

120,1020 and1220 may be delivered to the treatment site without the aid of theguidewire1736 and/or guide sheath.

Image guidance, e.g., computed tomography (CT), fluoroscopy, intravascular ultrasound (IVUS), optical coherence tomography (OCT), intracardiac echocardiography (ICE), or another suitable guidance modality, or combinations thereof, may be used to aid the clinician's positioning and manipulation of the

neuromodulation assemblies

120,1020 and1220. For example, a fluoroscopy system (e.g., including a flat-panel detector, x-ray, or c-arm) can be rotated to accurately visualize and identify the target treatment site. In other embodiments, the treatment site can be determined using IVUS, OCT, and/or other suitable image mapping modalities that can correlate the target treatment site with an identifiable anatomical structure (e.g., a spinal feature) and/or a radiopaque ruler (e.g., positioned under or on the patient) before delivering the

neuromodulation assemblies

120,1020 and1220. Further, in some embodiments, image guidance components (e.g., IVUS, OCT) may be integrated with theneuromodulation device1602 and/or run in parallel with theneuromodulation device1602 to provide image guidance during positioning of

neuromodulation assemblies

120,1020 and1220. For example, image guidance components (e.g., IVUS or OCT) can be coupled to

neuromodulation assemblies

120,1020 and1220 to provide three-dimensional images of the vasculature proximate the treatment site to facilitate positioning or deploying the multi-electrode assembly within the target renal vascular structure.

Energy from theenergy delivery elements124 may then be applied to target tissue to induce one or more desired neuromodulating effects on localized regions of the renal artery RA and adjacent regions of the renal plexus RP, which lay intimately within, adjacent to, or in close proximity to the adventitia of the renal artery RA. The purposeful application of the energy may achieve neuromodulation along all or at least a portion of the renal plexus RP. The neuromodulating effects are generally a function of, at least in part, power, time, contact between the energy delivery elements and the vessel wall, and blood flow through the vessel. The neuromodulating effects may include denervation, thermal ablation, and/or non-ablative thermal alteration or damage (e.g., via sustained heating and/or resistive heating). Desired thermal heating effects may include raising the temperature of target neural fibers above a desired threshold to achieve non-ablative thermal alteration, or above a higher temperature to achieve ablative thermal alteration. For example, the target temperature may be above body temperature (e.g., approximately 37° C.) but less than about 45° C. for non-ablative thermal alteration, or the target temperature may be about 45° C. or higher for the ablative thermal alteration. Desired non-thermal neuromodulation effects may include altering the electrical signals transmitted in a nerve.

Hypothermic effects may also provide neuromodulation. For example, a cryotherapeutic applicator may be used to cool tissue at a treatment site to provide therapeutically-effective direct cell injury (e.g., necrosis), vascular injury (e.g., starving the cell from nutrients by damaging supplying blood vessels), and sublethal hypothermia with subsequent apoptosis. Exposure to cryotherapeutic cooling can cause acute cell death (e.g., immediately after exposure) and/or delayed cell death (e.g., during tissue thawing and subsequent hyperperfusion). Embodiments of the present technology can include cooling a structure at or near an inner surface of a renal artery wall such that proximate (e.g., adjacent) tissue is effectively cooled to a depth where sympathetic renal nerves reside. For example, the cooling structure is cooled to the extent that it causes therapeutically effective, cryogenic renal-nerve modulation. Sufficiently cooling at least a portion of a sympathetic renal nerve is expected to slow or potentially block conduction of neural signals to produce a prolonged or permanent reduction in renal sympathetic activity.

III. Renal Neuromodulation

Renal neuromodulation is the partial or complete incapacitation or other effective disruption of nerves of the kidneys (e.g., nerves terminating in the kidneys or in structures closely associated with the kidneys). In particular, renal neuromodulation can include inhibiting, reducing, and/or blocking neural communication along neural fibers (e.g., efferent and/or afferent neural fibers) of the kidneys. Such incapacitation can be long-term (e.g., permanent or for periods of months, years, or decades) or short-term (e.g., for periods of minutes, hours, days, or weeks). Renal neuromodulation is expected to contribute to the systemic reduction of sympathetic tone or drive and/or to benefit at least some specific organs and/or other bodily structures innervated by sympathetic nerves. Accordingly, renal neuromodulation is expected to be useful in treating clinical conditions associated with systemic sympathetic over activity or hyperactivity, particularly conditions associated with central sympathetic overstimulation. For example, renal neuromodulation is expected to efficaciously treat hypertension, heart failure, acute myocardial infarction, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic and end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, polycystic kidney disease, polycystic ovary syndrome, osteoporosis, erectile dysfunction, and sudden death, among other conditions.

Renal neuromodulation can be electrically-induced, thermally-induced, chemically-induced, or induced in another suitable manner or combination of manners at one or more suitable treatment sites during a treatment procedure. The treatment site can be within or otherwise proximate to a renal lumen (e.g., a renal artery, a ureter, a renal pelvis, a major renal calyx, a minor renal calyx, or another suitable structure), and the treated tissue can include tissue at least proximate to a wall of the renal lumen. For example, with regard to a renal artery, a treatment procedure can include modulating nerves in the renal plexus, which lay intimately within or adjacent to the adventitia of the renal artery.

Renal neuromodulation can include a cryotherapeutic treatment modality alone or in combination with another treatment modality. Cryotherapeutic treatment can include cooling tissue at a treatment site in a manner that modulates neural function. For example, sufficiently cooling at least a portion of a sympathetic renal nerve can slow or potentially block conduction of neural signals to produce a prolonged or permanent reduction in renal sympathetic activity. This effect can occur as a result of cryotherapeutic tissue damage, which can include, for example, direct cell injury (e.g., necrosis), vascular or luminal injury (e.g., starving cells from nutrients by damaging supplying blood vessels), and/or sublethal hypothermia with subsequent apoptosis. Exposure to cryotherapeutic cooling can cause acute cell death (e.g., immediately after exposure) and/or delayed cell death (e.g., during tissue thawing and subsequent hyperperfusion). Neuromodulation using a cryotherapeutic treatment in accordance with embodiments of the present technology can include cooling a structure proximate an inner surface of a body lumen wall such that tissue is effectively cooled to a depth where sympathetic renal nerves reside. For example, in some embodiments, a cooling assembly of a cryotherapeutic device can be cooled to the extent that it causes therapeutically-effective, cryogenic renal neuromodulation. In other embodiments, a cryotherapeutic treatment modality can include cooling that is not configured to cause neuromodulation. For example, the cooling can be at or above cryogenic temperatures and can be used to control neuromodulation via another treatment modality (e.g., to protect tissue from neuromodulating energy).

Renal neuromodulation can include an electrode-based or transducer-based treatment modality alone or in combination with another treatment modality. Electrode-based or transducer-based treatment can include delivering electricity and/or another form of energy to tissue at a treatment location to stimulate and/or heat the tissue in a manner that modulates neural function. For example, sufficiently stimulating and/or heating at least a portion of a sympathetic renal nerve can slow or potentially block conduction of neural signals to produce a prolonged or permanent reduction in renal sympathetic activity. A variety of suitable types of energy can be used to stimulate and/or heat tissue at a treatment location. For example, neuromodulation in accordance with embodiments of the present technology can include delivering RF energy, pulsed energy, microwave energy, optical energy, focused ultrasound energy (e.g., high-intensity focused ultrasound energy), or another suitable type of energy alone or in combination. An electrode or transducer used to deliver this energy can be used alone or with other electrodes or transducers in a multi-electrode or multi-transducer array. Furthermore, the energy can be applied from within the body (e.g., within the vasculature or other body lumens in a catheter-based approach) and/or from outside the body (e.g., via an applicator positioned outside the body). Furthermore, energy can be used to reduce damage to non-targeted tissue when targeted tissue adjacent to the non-targeted tissue is subjected to neuromodulating cooling.

Neuromodulation using focused ultrasound energy (e.g., high-intensity focused ultrasound energy) can be beneficial relative to neuromodulation using other treatment modalities. Focused ultrasound is an example of a transducer-based treatment modality that can be delivered from outside the body. Focused ultrasound treatment can be performed in close association with imaging (e.g., magnetic resonance, computed tomography, fluoroscopy, ultrasound (e.g., intravascular or intraluminal), optical coherence tomography, or another suitable imaging modality). For example, imaging can be used to identify an anatomical position of a treatment location (e.g., as a set of coordinates relative to a reference point). The coordinates can then entered into a focused ultrasound device configured to change the power, angle, phase, or other suitable parameters to generate an ultrasound focal zone at the location corresponding to the coordinates. The focal zone can be small enough to localize therapeutically-effective heating at the treatment location while partially or fully avoiding potentially harmful disruption of nearby structures. To generate the focal zone, the ultrasound device can be configured to pass ultrasound energy through a lens, and/or the ultrasound energy can be generated by a curved transducer or by multiple transducers in a phased array (curved or straight).

Heating effects of electrode-based or transducer-based treatment can include ablation and/or non-ablative alteration or damage (e.g., via sustained heating and/or resistive heating). For example, a treatment procedure can include raising the temperature of target neural fibers to a target temperature above a first threshold to achieve non-ablative alteration, or above a second, higher threshold to achieve ablation. The target temperature can be higher than about body temperature (e.g., about 37° C.) but less than about 45° C. for non-ablative alteration, and the target temperature can be higher than about 45° C. for ablation. Heating tissue to a temperature between about body temperature and about 45° C. can induce non-ablative alteration, for example, via moderate heating of target neural fibers or of vascular or luminal structures that perfuse the target neural fibers. In cases where vascular structures are affected, the target neural fibers can be denied perfusion resulting in necrosis of the neural tissue. Heating tissue to a target temperature higher than about 45° C. (e.g., higher than about 60° C.) can induce ablation, for example, via substantial heating of target neural fibers or of vascular or luminal structures that perfuse the target fibers. In some patients, it can be desirable to heat tissue to temperatures that are sufficient to ablate the target neural fibers or the vascular or luminal structures, but that are less than about 90° C. (e.g., less than about 85° C., less than about 80° C., or less than about 75° C.).

Renal neuromodulation can include a chemical-based treatment modality alone or in combination with another treatment modality. Neuromodulation using chemical-based treatment can include delivering one or more chemicals (e.g., drugs or other agents) to tissue at a treatment location in a manner that modulates neural function. The chemical, for example, can be selected to affect the treatment location generally or to selectively affect some structures at the treatment location over other structures. The chemical, for example, can be guanethidine, ethanol, phenol, a neurotoxin, or another suitable agent selected to alter, damage, or disrupt nerves. A variety of suitable techniques can be used to deliver chemicals to tissue at a treatment location. For example, chemicals can be delivered via one or more needles originating outside the body or within the vasculature or other body lumens. In an intravascular example, a catheter can be used to intravascularly position a therapeutic element including a plurality of needles (e.g., micro-needles) that can be retracted or otherwise blocked prior to deployment. In other embodiments, a chemical can be introduced into tissue at a treatment location via simple diffusion through a body lumen wall, electrophoresis, or another suitable mechanism. Similar techniques can be used to introduce chemicals that are not configured to cause neuromodulation, but rather to facilitate neuromodulation via another treatment modality.

IV. Related Anatomy and Physiology

As noted previously, the sympathetic nervous system (SNS) is a branch of the autonomic nervous system along with the enteric nervous system and parasympathetic nervous system. It is always active at a basal level (called sympathetic tone) and becomes more active during times of stress. Like other parts of the nervous system, the sympathetic nervous system operates through a series of interconnected neurons. Sympathetic neurons are frequently considered part of the peripheral nervous system (PNS), although many lie within the central nervous system (CNS). Sympathetic neurons of the spinal cord (which is part of the CNS) communicate with peripheral sympathetic neurons via a series of sympathetic ganglia. Within the ganglia, spinal cord sympathetic neurons join peripheral sympathetic neurons through synapses. Spinal cord sympathetic neurons are therefore called presynaptic (or preganglionic) neurons, while peripheral sympathetic neurons are called postsynaptic (or postganglionic) neurons.

At synapses within the sympathetic ganglia, preganglionic sympathetic neurons release acetylcholine, a chemical messenger that binds and activates nicotinic acetylcholine receptors on postganglionic neurons. In response to this stimulus, postganglionic neurons principally release noradrenaline (norepinephrine). Prolonged activation may elicit the release of adrenaline from the adrenal medulla.

Once released, norepinephrine and epinephrine bind adrenergic receptors on peripheral tissues. Binding to adrenergic receptors causes a neuronal and hormonal response. The physiologic manifestations include pupil dilation, increased heart rate, occasional vomiting, and increased blood pressure. Increased sweating is also seen due to binding of cholinergic receptors of the sweat glands.

The sympathetic nervous system is responsible for up- and down-regulating many homeostatic mechanisms in living organisms. Fibers from the SNS innervate tissues in almost every organ system, providing at least some regulatory function to physiological features as diverse as pupil diameter, gut motility, and urinary output. This response is also known as sympatho-adrenal response of the body, as the preganglionic sympathetic fibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine, which activates the secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine). Therefore, this response that acts primarily on the cardiovascular system is mediated directly via impulses transmitted through the sympathetic nervous system and indirectly via catecholamines secreted from the adrenal medulla.

Science typically looks at the SNS as an automatic regulation system, that is, one that operates without the intervention of conscious thought. Some evolutionary theorists suggest that the sympathetic nervous system operated in early organisms to maintain survival as the sympathetic nervous system is responsible for priming the body for action. One example of this priming is in the moments before waking, in which sympathetic outflow spontaneously increases in preparation for action.

A. The Sympathetic Chain

As shown inFIG. 18, the SNS provides a network of nerves that allows the brain to communicate with the body. Sympathetic nerves originate inside the vertebral column, toward the middle of the spinal cord in the intermediolateral cell column (or lateral horn), beginning at the first thoracic segment of the spinal cord and are thought to extend to the second or third lumbar segments. Because its cells begin in the thoracic and lumbar regions of the spinal cord, the SNS is said to have a thoracolumbar outflow. Axons of these nerves leave the spinal cord through the anterior rootlet/root. They pass near the spinal (sensory) ganglion, where they enter the anterior rami of the spinal nerves. However, unlike somatic innervation, they quickly separate out through white rami connectors which connect to either the paravertebral (which lie near the vertebral column) or prevertebral (which lie near the aortic bifurcation) ganglia extending alongside the spinal column.

In order to reach the target organs and glands, the axons should travel long distances in the body, and, to accomplish this, many axons relay their message to a second cell through synaptic transmission. The ends of the axons link across a space, the synapse, to the dendrites of the second cell. The first cell (the presynaptic cell) sends a neurotransmitter across the synaptic cleft where it activates the second cell (the postsynaptic cell). The message is then carried to the final destination.

In the SNS and other components of the peripheral nervous system, these synapses are made at sites called ganglia, discussed above. The cell that sends its fiber is called a preganglionic cell, while the cell whose fiber leaves the ganglion is called a postganglionic cell. As mentioned previously, the preganglionic cells of the SNS are located between the first thoracic (T1) segment and third lumbar (L3) segments of the spinal cord. Postganglionic cells have their cell bodies in the ganglia and send their axons to target organs or glands.

The ganglia include not just the sympathetic trunks but also the cervical ganglia (superior, middle and inferior), which sends sympathetic nerve fibers to the head and thorax organs, and the celiac and mesenteric ganglia (which send sympathetic fibers to the gut).

1. Innervation of the Kidneys

AsFIG. 19 shows, the kidney is innervated by the renal plexus (RP), which is intimately associated with the renal artery. The renal plexus (RP) is an autonomic plexus that surrounds the renal artery and is embedded within the adventitia of the renal artery. The renal plexus (RP) extends along the renal artery until it arrives at the substance of the kidney. Fibers contributing to the renal plexus (RP) arise from the celiac ganglion, the superior mesenteric ganglion, the aorticorenal ganglion and the aortic plexus. The renal plexus (RP), also referred to as the renal nerve, is predominantly comprised of sympathetic components. There is no (or at least very minimal) parasympathetic innervation of the kidney.

Preganglionic neuronal cell bodies are located in the intermediolateral cell column of the spinal cord. Preganglionic axons pass through the paravertebral ganglia (they do not synapse) to become the lesser splanchnic nerve, the least splanchnic nerve, first lumbar splanchnic nerve, second lumbar splanchnic nerve, and travel to the celiac ganglion, the superior mesenteric ganglion, and the aorticorenal ganglion. Postganglionic neuronal cell bodies exit the celiac ganglion, the superior mesenteric ganglion, and the aorticorenal ganglion to the renal plexus (RP) and are distributed to the renal vasculature.

2. Renal Sympathetic Neural Activity

Messages travel through the SNS in a bidirectional flow. Efferent messages may trigger changes in different parts of the body simultaneously. For example, the sympathetic nervous system may accelerate heart rate; widen bronchial passages; decrease motility (movement) of the large intestine; constrict blood vessels; increase peristalsis in the esophagus; cause pupil dilation, piloerection (goose bumps) and perspiration (sweating); and raise blood pressure. Afferent messages carry signals from various organs and sensory receptors in the body to other organs and, particularly, the brain.

Hypertension, heart failure and chronic kidney disease are a few of many disease states that result from chronic activation of the SNS, especially the renal sympathetic nervous system. Chronic activation of the SNS is a maladaptive response that drives the progression of these disease states. Pharmaceutical management of the renin-angiotensin-aldosterone system (RAAS) has been a longstanding, but somewhat ineffective, approach for reducing over-activity of the SNS.

As mentioned above, the renal sympathetic nervous system has been identified as a major contributor to the complex pathophysiology of hypertension, states of volume overload (such as heart failure), and progressive renal disease, both experimentally and in humans. Studies employing radiotracer dilution methodology to measure overflow of norepinephrine from the kidneys to plasma revealed increased renal norepinephrine (NE) spillover rates in patients with essential hypertension, particularly so in young hypertensive subjects, which in concert with increased NE spillover from the heart, is consistent with the hemodynamic profile typically seen in early hypertension and characterized by an increased heart rate, cardiac output, and renovascular resistance. It is now known that essential hypertension is commonly neurogenic, often accompanied by pronounced sympathetic nervous system overactivity.

Activation of cardiorenal sympathetic nerve activity is even more pronounced in heart failure, as demonstrated by an exaggerated increase of NE overflow from the heart and the kidneys to plasma in this patient group. In line with this notion is the recent demonstration of a strong negative predictive value of renal sympathetic activation on all-cause mortality and heart transplantation in patients with congestive heart failure, which is independent of overall sympathetic activity, glomerular filtration rate, and left ventricular ejection fraction. These findings support the notion that treatment regimens that are designed to reduce renal sympathetic stimulation have the potential to improve survival in patients with heart failure.

Both chronic and end stage renal disease are characterized by heightened sympathetic nervous activation. In patients with end stage renal disease, plasma levels of norepinephrine above the median have been demonstrated to be predictive for both all-cause death and death from cardiovascular disease. This is also true for patients suffering from diabetic or contrast nephropathy. There is compelling evidence suggesting that sensory afferent signals originating from the diseased kidneys are major contributors to initiating and sustaining elevated central sympathetic outflow in this patient group; this facilitates the occurrence of the well-known adverse consequences of chronic sympathetic over activity, such as hypertension, left ventricular hypertrophy, ventricular arrhythmias, sudden cardiac death, insulin resistance, diabetes, and metabolic syndrome.

(i) Renal Sympathetic Efferent Activity

Sympathetic nerves to the kidneys terminate in the blood vessels, the juxtaglomerular apparatus and the renal tubules. Stimulation of the renal sympathetic nerves causes increased renin release, increased sodium (Na⁺) reabsorption, and a reduction of renal blood flow. These components of the neural regulation of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone and clearly contribute to the rise in blood pressure in hypertensive patients. The reduction of renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome, which is renal dysfunction as a progressive complication of chronic heart failure, with a clinical course that typically fluctuates with the patient's clinical status and treatment. Pharmacologic strategies to thwart the consequences of renal efferent sympathetic stimulation include centrally acting sympatholytic drugs, beta blockers (intended to reduce renin release), angiotensin converting enzyme inhibitors and receptor blockers (intended to block the action of angiotensin II and aldosterone activation consequent to renin release) and diuretics (intended to counter the renal sympathetic mediated sodium and water retention). However, the current pharmacologic strategies have significant limitations including limited efficacy, compliance issues, side effects and others.

(ii) Renal Sensory Afferent Nerve Activity

The kidneys communicate with integral structures in the central nervous system via renal sensory afferent nerves. Several forms of “renal injury” may induce activation of sensory afferent signals. For example, renal ischemia, reduction in stroke volume or renal blood flow, or an abundance of adenosine enzyme may trigger activation of afferent neural communication. As shown inFIGS. 20 and 21, this afferent communication might be from the kidney to the brain or might be from one kidney to the other kidney (via the central nervous system). These afferent signals are centrally integrated and may result in increased sympathetic outflow. This sympathetic drive is directed towards the kidneys, thereby activating the RAAS and inducing increased renin secretion, sodium retention, volume retention and vasoconstriction. Central sympathetic over activity also impacts other organs and bodily structures innervated by sympathetic nerves such as the heart and the peripheral vasculature, resulting in the described adverse effects of sympathetic activation, several aspects of which also contribute to the rise in blood pressure.

The physiology therefore suggests that (i) modulation of tissue with efferent sympathetic nerves will reduce inappropriate renin release, salt retention, and reduction of renal blood flow, and that (ii) modulation of tissue with afferent sensory nerves will reduce the systemic contribution to hypertension and other disease states associated with increased central sympathetic tone through its direct effect on the posterior hypothalamus as well as the contralateral kidney. In addition to the central hypotensive effects of afferent renal denervation, a desirable reduction of central sympathetic outflow to various other sympathetically innervated organs such as the heart and the vasculature is anticipated.

B. Additional Clinical Benefits of Renal Denervation

As provided above, renal denervation is likely to be valuable in the treatment of several clinical conditions characterized by increased overall and particularly renal sympathetic activity such as hypertension, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, and sudden death. Since the reduction of afferent neural signals contributes to the systemic reduction of sympathetic tone/drive, renal denervation might also be useful in treating other conditions associated with systemic sympathetic hyperactivity. Accordingly, renal denervation may also benefit other organs and bodily structures innervated by sympathetic nerves, including those identified inFIG. 18. For example, as previously discussed, a reduction in central sympathetic drive may reduce the insulin resistance that afflicts people with metabolic syndrome and Type II diabetics. Additionally, patients with osteoporosis are also sympathetically activated and might also benefit from the down regulation of sympathetic drive that accompanies renal denervation.

C. Achieving Intravascular Access to the Renal Artery

In accordance with the present technology, neuromodulation of a left and/or right renal plexus (RP), which is intimately associated with a left and/or right renal artery, may be achieved through intravascular access. AsFIG. 22 shows, blood moved by contractions of the heart is conveyed from the left ventricle of the heart by the aorta. The aorta descends through the thorax and branches into the left and right renal arteries. Below the renal arteries, the aorta bifurcates at the left and right iliac arteries. The left and right iliac arteries descend, respectively, through the left and right legs and join the left and right femoral arteries.

AsFIG. 23 shows, the blood collects in veins and returns to the heart, through the femoral veins into the iliac veins and into the inferior vena cava. The inferior vena cava branches into the left and right renal veins. Above the renal veins, the inferior vena cava ascends to convey blood into the right atrium of the heart. From the right atrium, the blood is pumped through the right ventricle into the lungs, where it is oxygenated. From the lungs, the oxygenated blood is conveyed into the left atrium. From the left atrium, the oxygenated blood is conveyed by the left ventricle back to the aorta.

As will be described in greater detail later, the femoral artery may be accessed and cannulated at the base of the femoral triangle just inferior to the midpoint of the inguinal ligament. A catheter may be inserted percutaneously into the femoral artery through this access site, passed through the iliac artery and aorta, and placed into either the left or right renal artery. This comprises an intravascular path that offers minimally invasive access to a respective renal artery and/or other renal blood vessels.

The wrist, upper arm, and shoulder region provide other locations for introduction of catheters into the arterial system. For example, catheterization of either the radial, brachial, or axillary artery may be utilized in select cases. Catheters introduced via these access points may be passed through the subclavian artery on the left side (or via the subclavian and brachiocephalic arteries on the right side), through the aortic arch, down the descending aorta and into the renal arteries using standard angiographic technique.

D. Properties and Characteristics of the Renal Vasculature

Since neuromodulation of a left and/or right renal plexus (RP) may be achieved in accordance with the present technology through intravascular access, properties and characteristics of the renal vasculature may impose constraints upon and/or inform the design of apparatus, systems, and methods for achieving such renal neuromodulation. Some of these properties and characteristics may vary across the patient population and/or within a specific patient across time, as well as in response to disease states, such as hypertension, chronic kidney disease, vascular disease, end-stage renal disease, insulin resistance, diabetes, metabolic syndrome, etc. These properties and characteristics, as explained herein, may have bearing on the efficacy of the procedure and the specific design of the intravascular device. Properties of interest may include, for example, material/mechanical, spatial, fluid dynamic/hemodynamic and/or thermodynamic properties.

As discussed previously, a catheter may be advanced percutaneously into either the left or right renal artery via a minimally invasive intravascular path. However, minimally invasive renal arterial access may be challenging, for example, because as compared to some other arteries that are routinely accessed using catheters, the renal arteries are often extremely tortuous, may be of relatively small diameter, and/or may be of relatively short length. Furthermore, renal arterial atherosclerosis is common in many patients, particularly those with cardiovascular disease. Renal arterial anatomy also may vary significantly from patient to patient, which further complicates minimally invasive access. Significant inter-patient variation may be seen, for example, in relative tortuosity, diameter, length, and/or atherosclerotic plaque burden, as well as in the take-off angle at which a renal artery branches from the aorta. Apparatus, systems and methods for achieving renal neuromodulation via intravascular access should account for these and other aspects of renal arterial anatomy and its variation across the patient population when minimally invasively accessing a renal artery.

In addition to complicating renal arterial access, specifics of the renal anatomy also complicate establishment of stable contact between neuromodulatory apparatus and a luminal surface or wall of a renal artery. For example, navigation can be impeded by the tight space within a renal artery, as well as tortuosity of the artery. Furthermore, establishing consistent contact is complicated by patient movement, respiration, and/or the cardiac cycle because these factors may cause significant movement of the renal artery relative to the aorta, and the cardiac cycle may transiently distend the renal artery (i.e. cause the wall of the artery to pulse).

Even after accessing a renal artery and facilitating stable contact between neuromodulatory apparatus and a luminal surface of the artery, nerves in and around the adventia of the artery should be safely modulated via the neuromodulatory apparatus. Effectively applying thermal treatment from within a renal artery is non-trivial given the potential clinical complications associated with such treatment. For example, the intima and media of the renal artery are highly vulnerable to thermal injury. As discussed in greater detail below, the intima-media thickness separating the vessel lumen from its adventitia means that target renal nerves may be multiple millimeters distant from the luminal surface of the artery. Sufficient energy should be delivered to or heat removed from the target renal nerves to modulate the target renal nerves without excessively cooling or heating the vessel wall to the extent that the wall is frozen, desiccated, or otherwise potentially affected to an undesirable extent. A potential clinical complication associated with excessive heating is thrombus formation from coagulating blood flowing through the artery. Given that this thrombus may cause a kidney infarct, thereby causing irreversible damage to the kidney, thermal treatment from within the renal artery should be applied carefully. Accordingly, the complex fluid mechanics and thermodynamic conditions present in the renal artery during treatment, particularly those that may impact heat transfer dynamics at the treatment site, may be important in applying energy (e.g., heating thermal energy) and/or removing heat from the tissue (e.g., cooling thermal conditions) from within the renal artery.

The neuromodulatory apparatus should also be configured to allow for adjustable positioning and repositioning of the energy delivery element within the renal artery since location of treatment may also impact clinical efficacy. For example, it may be tempting to apply a full circumferential treatment from within the renal artery given that the renal nerves may be spaced circumferentially around a renal artery. In some situations, a full-circle lesion likely resulting from a continuous circumferential treatment may be potentially related to renal artery stenosis. Therefore, the formation of more complex lesions along a longitudinal dimension of the renal artery and/or repositioning of the neuromodulatory apparatus to multiple treatment locations may be desirable. It should be noted, however, that a benefit of creating a circumferential ablation may outweigh the potential of renal artery stenosis or the risk may be mitigated with certain embodiments or in certain patients and creating a circumferential ablation could be a goal. Additionally, variable positioning and repositioning of the neuromodulatory apparatus may prove to be useful in circumstances where the renal artery is particularly tortuous or where there are proximal branch vessels off the renal artery main vessel, making treatment in certain locations challenging. Manipulation of a device in a renal artery should also consider mechanical injury imposed by the device on the renal artery. Motion of a device in an artery, for example by inserting, manipulating, negotiating bends and so forth, may contribute to dissection, perforation, denuding intima, or disrupting the interior elastic lamina.

Blood flow through a renal artery may be temporarily occluded for a short time with minimal or no complications. However, occlusion for a significant amount of time should be avoided because to prevent injury to the kidney such as ischemia. It could be beneficial to avoid occlusion all together or, if occlusion is beneficial to the embodiment, to limit the duration of occlusion, for example to 2-5 minutes.

Based on the above described challenges of (1) renal artery intervention, (2) consistent and stable placement of the treatment element against the vessel wall, (3) effective application of treatment across the vessel wall, (4) positioning and potentially repositioning the treatment apparatus to allow for multiple treatment locations, and (5) avoiding or limiting duration of blood flow occlusion, various independent and dependent properties of the renal vasculature that may be of interest include, for example, (a) vessel diameter, vessel length, intima-media thickness, coefficient of friction, and tortuosity; (b) distensibility, stiffness and modulus of elasticity of the vessel wall; (c) peak systolic, end-diastolic blood flow velocity, as well as the mean systolic-diastolic peak blood flow velocity, and mean/max volumetric blood flow rate; (d) specific heat capacity of blood and/or of the vessel wall, thermal conductivity of blood and/or of the vessel wall, and/or thermal convectivity of blood flow past a vessel wall treatment site and/or radiative heat transfer; (e) renal artery motion relative to the aorta induced by respiration, patient movement, and/or blood flow pulsatility; and (f) the take-off angle of a renal artery relative to the aorta. These properties will be discussed in greater detail with respect to the renal arteries. However, dependent on the apparatus, systems and methods utilized to achieve renal neuromodulation, such properties of the renal arteries, also may guide and/or constrain design characteristics.

As noted above, an apparatus positioned within a renal artery should conform to the geometry of the artery. Renal artery vessel diameter, D_RA, typically is in a range of about 2-10 mm, with most of the patient population having a D_RAof about 4 mm to about 8 mm and an average of about 6 mm. Renal artery vessel length, L_RA, between its ostium at the aorta/renal artery juncture and its distal branchings, generally is in a range of about 5-70 mm, and a significant portion of the patient population is in a range of about 20-50 mm. Since the target renal plexus is embedded within the adventitia of the renal artery, the composite Intima-Media Thickness, IMT, (i.e., the radial outward distance from the artery's luminal surface to the adventitia containing target neural structures) also is notable and generally is in a range of about 0.5-2.5 mm, with an average of about 1.5 mm. Although a certain depth of treatment is important to reach the target neural fibers, the treatment should not be too deep (e.g., >5 mm from inner wall of the renal artery) to avoid non-target tissue and anatomical structures such as the renal vein.

An additional property of the renal artery that may be of interest is the degree of renal motion relative to the aorta induced by respiration and/or blood flow pulsatility. A patient's kidney, which is located at the distal end of the renal artery, may move as much as 4″ cranially with respiratory excursion. This may impart significant motion to the renal artery connecting the aorta and the kidney, thereby requiring from the neuromodulatory apparatus a unique balance of stiffness and flexibility to maintain contact between the energy delivery element and the vessel wall during cycles of respiration. Furthermore, the take-off angle between the renal artery and the aorta may vary significantly between patients, and also may vary dynamically within a patient, e.g., due to kidney motion. The take-off angle generally may be in a range of about 30°-135°.

V. Additional Examples

The following examples are illustrative of several embodiments of the present technology:

1. A neuromodulation device, comprising:

- an elongated shaft having a distal portion with a cross-sectional area and a distal end, the cross-sectional area decreasing along a length of the distal portion toward the distal end;
- a neuromodulation assembly at the distal portion of the elongated shaft, the neuromodulation assembly comprising a plurality of energy delivery elements longitudinally spaced along the distal portion of the elongated shaft, wherein the plurality of energy delivery elements comprises at least a first electrode and a second electrode distal to the first electrode, and wherein the second electrode has a cross-sectional area less than that of the first electrode; and
- a plurality of pairs of lead wires carried by a portion of the elongated shaft, each pair of lead wires coupled to an energy delivery element,
- wherein the distal portion of the shaft is sized and shaped for delivery into a distal vascular portion of renal vasculature in a human.

2. The neuromodulation device of example 1 wherein the elongated shaft further comprises a braided circumferential wall, and wherein the lead wires are integrated with the braided circumferential wall.

3. The neuromodulation device of example 1 or example 2 wherein the cross-sectional area changes decrementally along the distal portion of the distal portion of the elongated shaft, and wherein the decrement relates to a combined cross-sectional area of a pair of the plurality of lead wires.

4. The neuromodulation device of any one of examples 1 to 3 wherein the distal portion of the elongated shaft comprises a greater quantity of lead wires at the first electrode than at the second electrode.

5. A neuromodulation device for delivering neuromodulation therapy in a vessel of a human patient, the neuromodulation device comprising:

- an elongated shaft having a distal portion with a first section and a second section distal to the first section, the first section having a first outer cross-sectional dimension and the second section having a second outer cross-sectional dimension less than the second outer cross-sectional dimension;
- a neuromodulation assembly at the distal portion of the elongated shaft, the neuromodulation assembly comprising—
  - a first energy delivery element at the first section of the elongated shaft; and
  - a second energy delivery element at the second section of the elongated shaft.

6. The neuromodulation device of example 5, further comprising:

- a first pair of lead wires electrically coupled to the first energy delivery element; and
- a second pair of lead wires electrically coupled to the second energy delivery element.

7. The neuromodulation device of example 5 or example 6 wherein:

- the first energy delivery element is a first electrode having a first outer cross-sectional dimension; and
- the second energy delivery element is a second electrode having a second outer cross-sectional dimension less than the first outer cross-sectional dimension of the first electrode.

8. The neuromodulation device of any one of examples 5 to 7 wherein the elongated shaft comprises a braid.

9. The neuromodulation device of any one of examples 5 to 8 wherein a first pair and a second pair of lead wires are incorporated into the braid.

10. The neuromodulation device of any one of examples 5 to 9 wherein the distal portion of the elongated shaft includes a shaped portion having a helical shape when the distal portion is in an expanded state.

11. The neuromodulation device of any one of examples 5 to 10 wherein the first section is a first shaped portion and the second section is a second shaped portion, and wherein the first and second shaped portions are helical when the distal portion is in an expanded state.

12. The neuromodulation device of any one of examples 5 to 11 wherein the first and second shaped sections are separated by a linear portion.

13. The neuromodulation device of any one of examples 5 to 12 wherein the elongated shaft comprises a guidewire lumen terminating in an opening at the distal portion of the elongated shaft, and wherein the neuromodulation device further comprises:

- a guidewire configured to extend through the guidewire lumen and through the opening; and
- a guidewire energy delivery element positioned at a distal section of the guidewire.

14. The neuromodulation device of example 13 wherein the guidewire further comprises at least one pair of lead wires electrically coupled to the guidewire energy delivery element.

15. The neuromodulation device of example 13 wherein the distal section of the guidewire defines the second section of the distal portion of the elongated shaft.

16. The neuromodulation device of example 13 wherein the guidewire has an outer cross-sectional dimension of 0.36 mm (0.014 inch).

17. The neuromodulation device of any one of examples 5 to 16, further comprising an atraumatic tip at the distal portion of the elongated shaft.

18. The neuromodulation device of any one of examples 5 to 17 wherein the distal portion of the elongated shaft has a distal end, and wherein the neuromodulation assembly further comprises a third energy delivery element at the distal end.

19. The neuromodulation device of any one of examples 5 to 18 wherein the elongated shaft further comprises a pre-formed nitinol core configured to impart a shape to the distal portion of the elongated shaft when the distal portion is in an expanded state.

20. The neuromodulation device of any one of examples 5 to 19 wherein the elongated shaft, the first energy delivery element, the second energy delivery element, the first pair of lead wires, and the second pair of lead wires are integral components of a single catheter.

21. The neuromodulation device of any one of examples 5 to 20 wherein the second energy delivery element is configured to deliver energy to ablate renal nerves along a distal vascular portion of a renal vascular structure of the patient.

22. The neuromodulation device of any one of examples 5 to 21 wherein the first outer cross-sectional dimension is a first outer diameter, and wherein the second outer cross-sectional dimension is a second outer diameter.

23. The neuromodulation device of any one of examples 5 to 22 wherein:

- the first and second sections of the distal portion of the elongated shaft are two of a plurality of sections of the distal portion of the elongated shaft;
- the first and second energy delivery elements are two of a plurality of energy delivery elements positioned at corresponding sections of the distal portion of the elongated shaft; and
- each section and each energy delivery element have an decrementally changing outer cross-sectional dimension as the sections are positioned closer to a distal end of the elongated shaft.

24. A method of administering neuromodulation therapy to a patient, the method comprising:

- delivering a distal portion of a neuromodulation device to a treatment site within a proximal vascular portion and a distal vascular portion of a renal vascular structure of a human, the distal portion of the neuromodulation device having a plurality of energy delivery elements spaced along a length of the distal portion, wherein the distal portion of the neuromodulation device has a first outer cross-sectional dimension at a first section of the distal portion and a second outer cross-sectional dimension at a second section of the distal portion, wherein the second section is distal to the first section, and wherein the first outer cross-sectional dimension is greater than the second outer cross-sectional dimension; and
- delivering neuromodulation energy to renal nerves within the proximal vascular structure and/or the distal vascular structure via at least one energy delivery element of the neuromodulation device.

25. The method of example 24, further comprising delivering a guidewire through a lumen of the neuromodulation device to the treatment site, wherein delivering neuromodulation energy to the renal nerves comprises delivering energy to the treatment site via at least one energy delivery element disposed on the guidewire.

26. The method of example 24 or example 25, further comprising transforming the distal portion of the neuromodulation device to a spiral shape at the treatment site such that at least one of the energy delivery elements contacts an inner wall of the distal vascular structure at the treatment site before delivering neuromodulation energy.

27. The method of any one of examples 24 to 26, further comprising delivering a guidewire to the treatment site within the distal vascular structure of the renal blood vessel.

28. The method of any one of examples 24 to 27 wherein delivering neuromodulation energy to renal nerves comprises delivering a first energy to energy delivery elements at the first section and a second energy to energy delivery elements at the second section, wherein the first energy is greater than the second energy.

29. The method of any one of examples 24 to 28, further comprising transforming the first section of the distal portion to a first spiral shape and the second section of the distal portion to a second spiral shape, wherein the first section is proximal to the second section, and wherein the first spiral shape has a first outer diameter and the second spiral shape has a second outer diameter less than the first outer diameter.

30. The method of any one of examples 24 to 29, further comprising positioning the second section of the distal portion of the neuromodulation device into a portion of the distal vascular structure having a diameter of less than 3 mm.

VI. Conclusion

From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the technology. Where the context permits, singular or plural terms may also include the plural or singular term, respectively.

Certain aspects of the present technology may take the form of computer-executable instructions, including routines executed by a controller or other data processor. In some embodiments, a controller or other data processor is specifically programmed, configured, and/or constructed to perform one or more of these computer-executable instructions. Furthermore, some aspects of the present technology may take the form of data (e.g., non-transitory data) stored or distributed on computer-readable media, including magnetic or optically readable and/or removable computer discs as well as media distributed electronically over networks. Accordingly, data structures and transmissions of data particular to aspects of the present technology are encompassed within the scope of the present technology. The present technology also encompasses methods of both programming computer-readable media to perform particular steps and executing the steps.

This disclosure is not intended to be exhaustive or to limit the present technology to the precise forms disclosed herein. Although specific embodiments are disclosed herein for illustrative purposes, various equivalent modifications are possible without deviating from the present technology, as those of ordinary skill in the relevant art will recognize. In some cases, well-known structures and functions have not been shown and/or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Although steps of methods may be presented herein in a particular order, in alternative embodiments the steps may have another suitable order. Similarly, certain aspects of the present technology disclosed in the context of particular embodiments can be combined or eliminated in other embodiments. Furthermore, while advantages associated with certain embodiments may have been disclosed in the context of those embodiments, other embodiments can also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages or other advantages disclosed herein to fall within the scope of the present technology. Accordingly, this disclosure and associated technology can encompass other embodiments not expressly shown and/or described herein.

Throughout this disclosure, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. Similarly, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the terms “comprising” and the like are used throughout this disclosure to mean including at least the recited feature(s) such that any greater number of the same feature(s) and/or one or more additional types of features are not precluded. Directional terms, such as “upper,” “lower,” “front,” “back,” “vertical,” and “horizontal,” may be used herein to express and clarify the relationship between various elements. It should be understood that such terms do not denote absolute orientation. Reference herein to “one embodiment,” “an embodiment,” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. Furthermore, various particular features, structures, operations, or characteristics may be combined in any suitable manner in one or more embodiments.